If you think the futures price will go up, go long (buy and open positions), go up (sell) and close positions, and earn: price difference = close positions-open positions.
If you think the futures price will fall, short (sell the position), fall (buy) and close the position, and earn: price difference = opening price-closing price.
Therefore, "opening a position" refers to signing a sales contract with others (deposit is required), "closing a position" refers to canceling the contract by cash settlement (deposit is returned and trading proceeds are settled), and "closing a position" refers to closing the position on the same day (generally, closing fees are exempted. )。